The proposition of advanced design and conception method for traction machine thermal management by surrogate-supported optimization. This method provides systematical framework for searching and developing new thermal concept for electric traction machines. Systematical conception of novel direct oil cooling concept in coil area with high cooling performance. The machine prototype tests show continuous current density of up to 34.8 A/mm2, which is more than two times of the current density in existed standard water cooled traction machines with literature value of 15 A/mm2, and higher than the performance of other cooling concepts in the literature. The development with the proposed surrogate-supported optimization method is demonstrated on an example of high power density switched reluctance (SR) machine. Experimental results shows, the continuous power density of the machine with developed novel approach is increased to 6.5 times than the commonly used water jacket cooling design. With the cooling performance, the thermal energy can be reused to heat up transmission oil. This can reduce gearbox losses further by 12% in the drive cycle relevant operation point.weiterlesen